Extensible parameters meta formats have been introduced in the Linux
kernel v6.12 initially to support different revision of the RkISP1 ISP
implemented in different SoC. In order to avoid breaking userspace
everytime an ISP configuration block is added or modified in the uAPI
these new formats, which are versionated and extensible by their
definition have been introduced.

See for reference:
e9d05e9d5db1 ("media: uapi: rkisp1-config: Add extensible params format")
6c53a7b68c5d ("media: rkisp1: Implement extensible params support")

The Amlogic C3 ISP driver followed shortly, introducing an extensible
format for the ISP configuration:

6d406187ebc0 ("media: uapi: Add stats info and parameters buffer for C3 ISP")

with a very similar, if not identical, implementation of the routines to
validate and handle the ISP configuration in the ISP driver in the
c3-isp-params.c file.

fb2e135208f3 ("media: platform: Add C3 ISP driver")

With the recent upstreaming attempt of the Mali C55 ISP driver from Dan,
a third user of extensible parameters is going to be itroduced in the
kernel, duplicating again in the driver the procedure for validating and
handling the ISP configuration blocks

https://patchwork.linuxtv.org/project/linux-media/patch/20250624-c55-v10-15-54f3d4196990@ideasonboard.com/

To avoid duplicating again the validation routines and common types
definition, this series introduces v4l2-isp.c/.h for the kAPI
and v4l2-isp.h for the uAPI and re-organize the RkISP1
and Amlogic C3 drivers to use the common types and the helper validation
routines.

The v4l2-isp abstraction will be augmented to support statistcs as well.

If the here proposed approach is accepted, I propose to rebase the Mali
C55 driver on top of this series, to use the new common types and
helpers.

I have been able to test this on RkISP1 but not on C3.

Thanks
  j

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
Changes in v5:
- Move everything to v4l2-isp prefix except from format documentation
  which still is about 'extensible-parameters' (to be paired in future
  with extensbile-stats)
- Simplify documentation and move it part to the driver-api
  Documentation
- Remove 'group' and 'features' from the generic handlers definition and
  adjust rkisp1 accordingly
- Link to v4: https://lore.kernel.org/r/20250820-extensible-parameters-validation-v4-0-30fe5a99cb1f@ideasonboard.com

Changes in v4:
- Fix the definition of V4L2_PARAMS_FL_PLATFORM_FLAGS
- Add __counted_by() attribute to the data[] flexible-array member of
  v4l2_params_buffer
- Minor style change
- Link to v3: https://lore.kernel.org/r/20250819-extensible-parameters-validation-v3-0-9dc008348b30@ideasonboard.com

Changes in v3:
- Rebased on latest media-committers/next
- Take in Dan's suggestion in block size validation
- Documentation minor spelling fixes
- Link to v2: https://lore.kernel.org/r/20250710-extensible-parameters-validation-v2-0-7ec8918ec443@ideasonboard.com

Changes in v2:
- Make v4l2_params_buffer directly usable
- Centralize ENABLE/DISABLE flags definition and validation
- Take in Dan's v4l2_params_buffer_size()
- Allow blocks to only contain the header if they're going to be
  disabled
- Documentation fixes as reported by Nicolas
- Link to v1: https://lore.kernel.org/r/20250708-extensible-parameters-validation-v1-0-9fc27c9c728c@ideasonboard.com

---
Jacopo Mondi (8):
      media: uapi: Introduce V4L2 generic ISP types
      media: uapi: Convert RkISP1 to V4L2 extensible params
      media: uapi: Convert Amlogic C3 to V4L2 extensible params
      media: Documentation: uapi: Add V4L2 extensible parameters
      media: v4l2-core: Introduce v4l2-isp.c
      media: rkisp1: Use v4l2-isp for validation
      media: amlogic-c3: Use v4l2-isp for validation
      media: Documentation: kapi: Add v4l2 generic ISP support

 Documentation/driver-api/media/v4l2-core.rst       |   1 +
 Documentation/driver-api/media/v4l2-isp.rst        |  37 ++
 .../media/v4l/extensible-parameters.rst            |  97 +++++
 .../userspace-api/media/v4l/meta-formats.rst       |   1 +
 MAINTAINERS                                        |  10 +
 drivers/media/platform/amlogic/c3/isp/Kconfig      |   1 +
 .../media/platform/amlogic/c3/isp/c3-isp-params.c  | 248 ++++--------
 drivers/media/platform/rockchip/rkisp1/Kconfig     |   1 +
 .../media/platform/rockchip/rkisp1/rkisp1-params.c | 441 ++++++++++-----------
 drivers/media/v4l2-core/Kconfig                    |   4 +
 drivers/media/v4l2-core/Makefile                   |   1 +
 drivers/media/v4l2-core/v4l2-isp.c                 | 108 +++++
 include/media/v4l2-isp.h                           | 100 +++++
 include/uapi/linux/media/amlogic/c3-isp-config.h   |  86 +---
 include/uapi/linux/media/v4l2-isp.h                | 100 +++++
 include/uapi/linux/rkisp1-config.h                 | 104 +----
 16 files changed, 793 insertions(+), 547 deletions(-)
---
base-commit: 0e2ee70291e64a30fe36960c85294726d34a103e
change-id: 20250701-extensible-parameters-validation-c831f7f5cc0b

Best regards,
-- 
Jacopo Mondi <jacopo.mondi@ideasonboard.com>

Hi Jacopo,

On Mon, Sep 15, 2025 at 07:18:09PM +0200, Jacopo Mondi wrote:
> Extensible parameters meta formats have been introduced in the Linux
> kernel v6.12 initially to support different revision of the RkISP1 ISP
> implemented in different SoC. In order to avoid breaking userspace
> everytime an ISP configuration block is added or modified in the uAPI
> these new formats, which are versionated and extensible by their
> definition have been introduced.
> 
> See for reference:
> e9d05e9d5db1 ("media: uapi: rkisp1-config: Add extensible params format")
> 6c53a7b68c5d ("media: rkisp1: Implement extensible params support")
> 
> The Amlogic C3 ISP driver followed shortly, introducing an extensible
> format for the ISP configuration:
> 
> 6d406187ebc0 ("media: uapi: Add stats info and parameters buffer for C3 ISP")
> 
> with a very similar, if not identical, implementation of the routines to
> validate and handle the ISP configuration in the ISP driver in the
> c3-isp-params.c file.
> 
> fb2e135208f3 ("media: platform: Add C3 ISP driver")
> 
> With the recent upstreaming attempt of the Mali C55 ISP driver from Dan,
> a third user of extensible parameters is going to be itroduced in the
> kernel, duplicating again in the driver the procedure for validating and
> handling the ISP configuration blocks
> 
> https://patchwork.linuxtv.org/project/linux-media/patch/20250624-c55-v10-15-54f3d4196990@ideasonboard.com/
> 
> To avoid duplicating again the validation routines and common types
> definition, this series introduces v4l2-isp.c/.h for the kAPI
> and v4l2-isp.h for the uAPI and re-organize the RkISP1
> and Amlogic C3 drivers to use the common types and the helper validation
> routines.
> 
> The v4l2-isp abstraction will be augmented to support statistcs as well.
> 
> If the here proposed approach is accepted, I propose to rebase the Mali
> C55 driver on top of this series, to use the new common types and
> helpers.
> 
> I have been able to test this on RkISP1 but not on C3.

Thank you for working on this.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>

-- 
Kind regards,

Sakari Ailus